Traditionally, such fastenings are made by means of discrete fitted elements such as rivets, plastics material fasteners, or screws where the thread engages in a hole or opening in the support while the head holds captive the plastics part that is to be fixed thereto. Although that kind of assembly is easy to disassemble, it is expensive because it leads to making additional tooling. Furthermore, such fastening by means of discrete fitted elements costs a great deal of labor time.